The present invention relates to the control of printer ribbons in high speed printers, and especially to a printer ribbon anti-fold mechanism for preventing creasing or folding in the center of the ribbon riding on pairs of abutting rollers.
The present invention relates to high speed printers of the type having an on-the-fly, or fast moving character band having banks of hammers mounted adjacent thereto for hitting a character on the fast moving character band in the proper position as the character band moves thereby. This type of printer uses wide ribbons or carbon paper positioned to extend across the length of the character band so that simultaneous driving of hammer banks against characters in different positions on the character band will print a character on paper adjacent the ribbon. In high speed printers, the ribbon moves at a rapid speed through the printer to continuously place a fresh portion adjacent the character band as the hammers are fired.
It has been common in the past to provide a variety of mechanisms for controlling the skew of the ribbon, and this is accomplished by shifting rollers at a slight angle to shift the ribbon to one side or the other to maintain ribbon tracking and positioning relative to the hammers when ribbon motion occurs. A typical system for controlling ribbon skew utilizes skew drive motors rotating an eccentric cam, which displaces a skew arm assembly, which in turn is controlled by a microprocessor. The present invention, on the other hand, is used to maintain the wide ribbon taut without creases or folds, especially between abutting rollers, which fold would interfere with the printing operation of the printer. Accordingly, the present invention has a mechanism operating two separate pairs of rollers which the ribbon is riding on to maintain the ribbon taut even as it is shifted by separate control mechanisms to position the ribbon relative to the hammers.